Plating diaphragm, plating method, and plating apparatus

ABSTRACT

Provided is a plating diaphragm used for a plating method including disposing the plating diaphragm between an anode and a substrate that is a cathode, applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm, and depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate, the plating diaphragm containing a base made of a polyolefin porous membrane, in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength is from 11 MPa to 300 MPa.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No. 2019-121200, filed Jun. 28, 2019, which is incorporated herein by reference.

BACKGROUND Technical Field

The present invention relates to a plating diaphragm, a plating method, and a plating apparatus.

Related Art

Conventionally, a technique has been proposed in which a metal film is formed by depositing a metal on a surface of a substrate.

As such a technique, for example, Patent Document 1 discloses a film forming apparatus for a metal film, which includes: an anode; a solid electrolyte membrane which is disposed between the anode and a substrate that is a cathode, and contains metal ions; a power supply which applies a voltage between the anode and the substrate; and a placing table on which the substrate is placed, in which a metal film is formed on a surface of the substrate.

The film forming apparatus for a metal film further includes a solution accommodation portion which accommodates a metal solution containing metal ions between the anode and the solid electrolyte membrane and a pressurizing portion which pressurizes the metal solution in the solution accommodation portion. The solid electrolyte membrane is pressurized by the liquid pressure of the metal solution pressurized by the pressurizing portion, and the surface of the substrate is pressed by the pressurized solid electrolyte membrane. Accordingly, the solid electrolyte membrane conforms to the surface of the substrate. The metal ions contained in the solid electrolyte membrane are reduced at the surface of the substrate by applying a voltage between the anode and the substrate, and a metal derived from the metal ions deposits, so that a metal film can be formed on the surface of the substrate.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent No. 6447575

SUMMARY OF THE INVENTION

However, in a conventional plating apparatus such as the film forming apparatus described in Patent Document 1, a fluororesin-based solid electrolyte membrane represented by Nafion (registered trademark) or the like is generally used. For example, when the fluororesin-based solid electrolyte membrane is disposed of by incineration or the like after use in plating, for example, an action on the impact of generated gas on the environment, a special treatment for performing a suitable disposal treatment, or the like may be required, and certain concerns may arise in disposal treatment.

The present disclosure has been made in view of the above.

A problem to be solved by the embodiments of the present invention is to provide a plating diaphragm, a plating method, and a plating apparatus in which a concern during disposal treatment is eliminated and plating can be formed suitably.

Specific means for achieving the object includes the following aspects.

<1> A plating diaphragm used for a plating method including disposing the plating diaphragm between an anode and a substrate that is a cathode, applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm, and depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate, the plating diaphragm comprising:

a base made of a polyolefin porous membrane,

wherein, in a case in which pure water is dropped on a surface (i.e., a main surface of the plating diaphragm), a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength is from 11 MPa to 300 MPa.

<2> The plating diaphragm according to <1>, wherein an average pore size of the plating diaphragm is from 5 nm to 300 nm.

<3> The plating diaphragm according to <1> or <2>, wherein a thickness of the plating diaphragm is from 8 μm to 200 μm.

<4> The plating diaphragm according to any one of <1> to <3>, wherein the base has a hydrophilic material on at least a portion of a main surface, a pore inner surface, or a combination thereof.

<5> The plating diaphragm according to <4>, wherein the hydrophilic material has at least one selected from the group consisting of a hydroxy group, a carbonyl group, a carboxy group, a formyl group, a sulfo group, a sulfonyl group, a thiol group, an amino group, a nitrile group, a nitro group, a pyrrolidone ring group, an ether bond and an amide bond.

<6> The plating diaphragm according to <4> or <5>, wherein the hydrophilic material includes an olefin/vinyl alcohol resin.

<7> The plating diaphragm according to any one of <1> to <6>, wherein the metal is at least one selected from the group consisting of nickel, zinc, copper, chromium, tin, silver, gold and lead.

<8> A plating method including:

disposing a plating diaphragm between an anode and a substrate that is a cathode;

applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm; and

depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate,

wherein the plating diaphragm comprises a base made of a polyolefin porous membrane, and

wherein, in a case in which pure water is dropped on a surface (i.e., a main surface) of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa.

<9> A plating apparatus including:

an anode;

a plating diaphragm that is disposed between the anode and a substrate, which is a cathode, and that contains metal ions; and

a power supply that applies a voltage between the anode and the substrate,

a metal that is derived from the metal ions being deposited on a surface of the substrate in contact with the plating diaphragm, to form a metal film on the surface of the substrate,

wherein the plating diaphragm comprises a base made of a polyolefin porous membrane, and in a case in which pure water is dropped on a surface (i.e., a main surface) of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa.

The embodiments of the present invention provide a plating diaphragm, a plating method, and a plating apparatus that can eliminate a concern during disposal treatment and can perform plating suitably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a film forming apparatus for a metal film according to an embodiment of the present disclosure;

FIG. 2 is a view for explaining formation of a metal film on a surface of a substrate using the film forming apparatus shown in FIG. 1;

FIG. 3 is a microscope photograph of an Ni film of Example 1;

FIG. 4 is a microscope photograph of a Cu film of Example 1;

FIG. 5 is a microscope photograph of the Ni film of Example 2;

FIG. 6 is a microscope photograph of the Cu film of Example 2;

FIG. 7 is a microscope photograph of the Ni film of Comparative Example 1;

FIG. 8 is a microscope photograph of the Cu film of Comparative Example 1;

FIG. 9 is a microscope photograph of the Ni film of Comparative Example 2;

FIG. 10 is a microscope photograph of the Cu film of Comparative Example 2;

FIG. 11 is a microscope photograph of the Ni film of Comparative Example 3; and

FIG. 12 is a microscope photograph of the Cu film of Comparative Example 3.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of a plating diaphragm, a plating method, and a plating apparatus according to the present disclosure will be sequentially described. However, the following description and Examples, which are specific aspects of the embodiments, illustrate the plating diaphragm, the plating method, and the plating apparatus according to the disclosure, and do not limit the scope of the disclosure.

In the present application, the numerical range denoted by using “to” represents the range inclusive of the number written before and after “to” as the minimum and maximum values. Regarding stepwise numerical ranges designated in the present disclosure, an upper or lower limit set forth in a certain numerical range may be replaced by an upper or lower limit of another stepwise numerical range described. Besides, an upper or lower limit set forth in a certain numerical range of the numerical ranges designated in the disclosure may be replaced by a value indicated in Examples.

In addition, with reference to a microporous polyolefin membrane, the term “longitudinal direction” means the direction of the length of the microporous polyolefin membrane that is produced in an elongated shape, while the term “width direction” means the direction that is perpendicular to the length direction of the microporous polyolefin membrane. Hereinafter, “width direction” is sometimes also referred to as “TD”, while “length direction” as “MD.”

In the present specification, the “process” refers not only to an independent process but also to a step that cannot be clearly distinguished from the other steps, as long as the intended aim of the process is achieved.

In the disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[Plating Diaphragm]

The plating diaphragm of the disclosure includes a base made of a polyolefin porous film and satisfies the following (1) contact angle and (2) tensile breaking strength.

(1) The contact angle θ is from 0° to 90°.

When pure water is dropped on a surface, the contact angle θ is an angle between a droplet and the surface when one second has passed since landing of the droplet of the pure water on the surface since landing of the pure water.

(2) The tensile breaking strength is from 11 MPa to 300 MPa.

The plating diaphragm of the disclosure is used for a plating method including disposing a plating diaphragm between an anode and a substrate that is a cathode, applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm, and depositing a metal derived from the metal ions in the plating diaphragm on the surface of the substrate, to form a metal film on the surface of the substrate.

The term “surface” in the plating diaphragm refers to a pair of the largest surfaces (i.e., main surfaces) in the diaphragm.

The details of an anode, a substrate which is a cathode, metal ions and metals, and a plating treatment such as a plating method will be described later in the section of the plating method, and the description thereof will be omitted.

Conventionally, as in Patent Document 1, for example, there has been known a film formation technique (so-called solid electrolyte deposition) in which an anode, a substrate which is a cathode, and a solid electrolyte membrane disposed between the anode and the substrate which is a cathode are provided, and a voltage is applied between the anode and the substrate to reduce metal ions included inside of the solid electrolyte membrane, and thus to deposit metal on a surface of the substrate, thereby forming a metal film on the surface of the substrate.

However, a fluororesin-based solid electrolyte membrane represented by Nafion or the like, which is generally used for solid electrolyte deposition as a solid electrolyte membrane, is expected to provide an alternative material for fluororesin for reasons such as improvement of the impact of generated gas on the environment or elimination of a load of a special treatment or the like for performing a suitable disposal treatment when the fluororesin-based solid electrolyte membrane is disposed of by incineration or the like after use.

The plating diaphragm of the disclosure is a porous film using polyolefin and is expected to be used as an alternative material such as a fluororesin. The plating diaphragm of the disclosure can solve disposal treatment problems and can achieve plating equal to or more than a solid electrolyte membrane such as Nafion that has been used conventionally.

For example, as in Patent Document 1, a membrane used for solid electrolyte deposition is required to have a membrane quality and an ion conduction performance that can seal a solution accommodation portion, which accommodates a metal solution (a so-called plating solution) containing metal ions, so as to prevent leakage of the metal solution in the solution accommodation portion. Thus, in reality, a solid electrolyte membrane has generally been adopted. On the other hand, for example, a porous membrane is generally known to have pores of a certain size, and therefore, the porous membrane is rarely used for an application requiring sealing of a solution.

Under such circumstances, it has been found that the polyolefin porous membrane having a specific contact angle θ and tensile breaking strength can exhibit both the sealing action and the ion conduction action of the accommodated solution and can be provided for solid electrolyte deposition.

That is, a conventional solid electrolyte membrane (such as Nafion) used for solid electrolyte deposition does not have pores allowing components larger in size than ions to pass therethrough, and for example, plating is performed by a mechanism that bonds metal ions to a sulfo group and conducts the metal ions. On the other hand, the porous membrane allows an aqueous solution containing the metal ions to reach a substrate without bonding the metal ions to the plating diaphragm and thereby can maintain an ion conduction action while having a certain sealing function. The plating diaphragm of the disclosure includes a base made of a polyolefin porous membrane, and the metal solution containing metal ions reaches the substrate as described above, whereby plating can be suitably performed.

Since the plating solution can be applied to both an aqueous solution containing an aqueous solvent containing no organic solvent and an aqueous solution containing a mixed solvent of an organic solvent and water, the versatility is high.

The solid electrolyte membrane used for solid electrolyte deposition generally has low mechanical strength. As a technique for increasing the mechanical strength, a technique for applying a water-repellent diaphragm is being studied. However, the water-repellent diaphragm has a mechanical strength because it has no hydrophilic ion channel structure, but has poor wettability to a plating bath. As a result, when the water-repellent diaphragm is applied to solid electrolyte deposition, film formation cannot be performed well.

The plating diaphragm of the disclosure has excellent mechanical strength because a membrane structure does not have an ion channel structure in which a hydrophilic region and a hydrophobic region coexist. Since a surface of the plating diaphragm of the disclosure is adjusted to be hydrophilic by adjusting the contact angle θ to a specific range, the surface also has high wettability to a plating bath, and the surface exhibits excellent film formability when applied to solid electrolyte deposition.

The plating diaphragm of the disclosure includes a base made of a polyolefin porous membrane.

The plating diaphragm of the disclosure has a contact angle θ of from 0° to 90° and has hydrophilicity satisfying the contact angle θ. The higher the hydrophilicity, the better permeability of a plating solution to the plating diaphragm.

From the viewpoint of satisfying the above range of the contact angle θ, the plating diaphragm of the disclosure may be, for example, a membrane obtained by performing a hydrophilic treatment on a base made of a polyolefin porous membrane.

The term “hydrophilicity” means that the contact angle θ is in the range of from 0° to 90°, and the term “hydrophilic treatment” means that the contact angle θ of the surface is adjusted in the range of from 0° to 90°.

The contact angle θ of from 0° to 90° means that having wettability to pure water and that the wettability is superior to liquid repellency.

The contact angle θ is preferably from 0° to 60°, more preferably from 0° to 50°, and still more preferably from 0° to 30° from the viewpoint of higher wettability to pure water and further enhancing uniformity of a surface structure of the plating diaphragm to be formed.

When pure water is dropped on a surface, the contact angle θ is the angle between a droplet and the surface after one second has passed since landing of the pure water, and is a value obtained by measuring a static contact angle with respect to a plating diaphragm in a dry state without pretreatment, using a fully automatic contact angle meter under the following conditions. For the measurement, for example, a fully automatic contact angle meter (DMo-701FE and Interface Measurement and Analysis System FAMAS) manufactured by Kyowa Interface Science, Inc can be used.

<Measurement Conditions>

-   -   Environment: in atmosphere at atmospheric pressure, 24° C., 60%         relative humidity     -   Measurement solution: pure water

—Hydrophilic Treatment—

Examples of hydrophilic treatment methods include a method of applying a hydrophilic material to a surface of a base made of a polyolefin porous membrane and a method of performing a surface treatment on the surface of the base made of the polyolefin porous membrane.

Details of the base made of the polyolefin porous membrane will be described later.

The hydrophilic treatment is preferably performed on at least a portion of at least one of a main surface and a pore inner surface of the base made of the polyolefin porous membrane, and more preferably performed on at least a portion of a main surface, a pore inner surface, or a combination thereof, of the base made of the polyolefin porous membrane.

The main surface of the base refers to a pair of the largest surfaces in a plate-like base such as a sheet or a film. The pore inner surface of the base refers to a surface inside a porous base.

As a method of applying the hydrophilic material to the surface of the base, a method of attaching the hydrophilic material to at least a main surface, a pore inner surface, or a combination thereof, of the base made of the polyolefin porous membrane may be mentioned.

Examples of the method of attachment include a method of applying a liquid containing a hydrophilic material and a method of dipping in the liquid containing the hydrophilic material.

Examples of the hydrophilic material include compounds having hydrophilicity, such as a hydrophilic resin and a surfactant.

The hydrophilic material used for the base may be one kind or two or more kinds.

Examples of the hydrophilic resin include resins having one or more hydrophilic groups selected from the group consisting of a hydroxy group, a carbonyl group, a carboxy group, a formyl group, a sulfo group, a sulfonyl group, a thiol group, an amino group, a nitrile group, a nitro group, a pyrrolidone ring group, an ether bond, and an amide bond.

As the hydrophilic group, a hydroxy group, a carboxy group, a sulfo group, a sulfonyl group, an amino group, and an ether bond are preferable in terms of easily giving a more hydrophilic property.

The hydrophilic resin is preferably a resin in which a main chain of a polymer is composed only of carbon atoms and which has at least one hydrophilic group selected from the group consisting of a hydroxy group, a carboxy group, and a sulfo group in a side chain.

Examples of the hydrophilic resin include a resin (e.g., polyethylene glycol, cellulose, etc.) containing not only a carbon atom but also an oxygen atom in the main chain of the polymer. However, a hydrophilic resin containing an oxygen atom in the main chain of the polymer tends to relatively easily come off from the porous base. From the viewpoint of making it unlikely for the resin to come off from the porous base, a resin in which the main chain of the polymer is composed of only carbon atoms is preferable, and a resin in which the main chain of the polymer is composed only of carbon atoms and which has at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, and a sulfo group in a side chain is more preferable.

The hydrophilic resin preferably contains at least one hydrophilic resin selected from the group consisting of polyvinyl alcohol, olefin/vinyl alcohol resin, acrylic/vinyl alcohol resin, methacryl/vinyl alcohol resin, vinylpyrrolidone/vinyl alcohol resin, polyacrylic acid, polymethacrylic acid, perfluorosulfonic acid resin, and polystyrene sulfonic acid. Among them, it is more preferable to contain the olefin/vinyl alcohol resin.

Examples of the olefin constituting the olefin/vinyl alcohol resin include ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, and decene. The olefin is preferably an olefin having from 2 to 6 carbon atoms, more preferably an α-olefin having from 2 to 6 carbon atoms, still more preferably an α-olefin having from 2 to 4 carbon atoms, and particularly preferably ethylene. The olefin unit contained in the olefin/vinyl alcohol resin may be one type or two or more types.

The olefin/vinyl alcohol resin may be a terpolymer having a monomer other than olefin and vinyl alcohol in its constituent unit.

Examples of the monomer other than olefin and vinyl alcohol include at least one acrylic monomer selected from the group consisting of (meth)acrylic acid, (meth)acrylate, and (meth)acrylic acid ester; and styrene-based monomers such as styrene, metachlorostyrene, parachlorostyrene, parafluorostyrene, paramethoxystyrene, meta-tert-butoxystyrene, para-tert-butoxystyrene, palavinylbenzoic acid, and paramethyl-α-methylstyrene.

One or two or more kinds of the other monomer units may be contained in the olefin/vinyl alcohol resin.

When the olefin/vinyl alcohol resin is the terpolymer having a monomer other than olefin and vinyl alcohol in its constituent unit, a total ratio of a constituent unit derived from olefin and a constituent unit derived from vinyl alcohol is preferably 85 mol % or more, more preferably 90 mol % or more, and still more preferably 95 mol % or more.

The olefin/vinyl alcohol resin in the disclosure is particularly preferably a binary copolymer in which the total ratio of the constituent unit derived from olefin and the constituent unit derived from vinyl alcohol is 100 mol %. Examples of the olefin/vinyl alcohol resin which is a binary copolymer include an ethylene/vinyl alcohol binary copolymer and a propylene/vinyl alcohol binary copolymer.

A ratio of the olefin unit in the olefin/vinyl alcohol resin is preferably from 20 mol % to 55 mol %. When the ratio of the olefin unit is 20 mol % or more, the olefin/vinyl alcohol resin is less likely to be dissolved in water. In this respect, the ratio of the olefin unit is more preferably 23 mol % or more, and still more preferably 25 mol % or more. When the ratio of the olefin unit is 55 mol % or less, the hydrophilicity of the olefin/vinyl alcohol resin is higher. In this respect, the ratio of the olefin unit is more preferably 52 mol % or less, and still more preferably 50 mol % or less.

As the olefin/vinyl alcohol resin, a commercially available product currently marketed may be used. Examples of the commercially available product include SOARNOL series manufactured by The Nippon Synthetic Chemical Industry Co., Ltd. and EVAL series manufactured by Kuraray Co., Ltd.

Examples of the hydrophilic resin include a hydrophilic resin obtained by graft-polymerizing a hydrophilic monomer on a surface of a porous base. In this case, the hydrophilic resin is in a form chemically bonded directly to the surface of the porous base. Examples of the hydrophilic monomer graft-polymerized on the surface of the porous base include acrylic acid, methacrylic acid, vinyl alcohol, N-vinyl-2-pyrrolidone, and vinyl sulfonic acid. From the viewpoint of productivity of the plating diaphragm, a configuration in which the hydrophilic resin is attached to the surface of the porous base by a coating method or the like (configuration in which the hydrophilic resin is not chemically bonded to the surface of the porous base) is more preferable than a configuration in which the hydrophilic resin is chemically bonded directly to the surface of the porous base as in the case of graft polymerization.

The amount of the hydrophilic resin attached to the porous base is, for example, from 0.01 g/m² to 10 g/m², may be from 0.05 g/m² to 8 g/m², or may be from 0.1 g/m² to 5 g/m². The amount of the hydrophilic resin attached to the porous base is a value (Wa−Wb) obtained by subtracting a basis weight Wb (g/m²) of the porous base from the basis weight Wa (g/m²) of the plating diaphragm.

As a surfactant, a known surfactant can be selected if appropriate and used, and an anionic surfactant and a cationic surfactant are preferred from the viewpoint of imparting the ion conduction action.

When a surfactant is used for the hydrophilic treatment of the porous base, the amount of the surfactant attached to the porous base is, for example, from 0.01 g/m² to 10 g/m², may be from 0.05 g/m² to 8 g/m², or may be from 0.1 g/m² to 5 g/m².

Examples of a method of performing a surface treatment on the surface of the base include a hydrophilic treatment by a plasma treatment, a corona treatment, a flame treatment, an ultraviolet irradiation treatment, or the like.

Conditions for the surface treatment may be selected if appropriate within the range of the contact angle θ described above.

—Base—

The base (hereinafter, also referred to as “porous base”) made of the polyolefin porous membrane in the disclosure refers to a base having pores or voids inside.

Examples of the porous base include a porous sheet made of a fibrous material, such as a nonwoven fabric or paper. As the porous base, from the viewpoints of thinning of a concentrated membrane according to the disclosure and high strength, a microporous membrane is preferred. A microporous membrane refers to a membrane having a large number of micropores inside, the micropores being connected to allow gas or liquid to pass therethrough from one side to the other side.

The porous base may be either hydrophilic or hydrophobic.

When the porous base is a hydrophobic base, it is preferable that the porous base is covered with a hydrophilic resin or that the surface of the porous base is treated to exhibit hydrophilicity.

The surface of the porous base may be further subjected to various surface treatments for the purpose of improving wettability of a coating solution used for covering the porous base with a hydrophilic resin. Examples of the surface treatment of the porous base include a corona treatment, a plasma treatment, a flame treatment, and an ultraviolet irradiation treatment.

[Physical Properties of Base]

From the viewpoint of having the tensile breaking strength in the above range and performing the sealing action on a metal solution (plating solution), the thickness of the porous base is preferably 10 μm or more, more preferably 15 μm or more, and still more preferably 20 μm or more. From the viewpoint of maintaining the property that the metal solution can reach the base by smearing while sealing the metal solution, the thickness of the porous base is preferably 180 μm or less, more preferably 150 μm or less, and still more preferably 120 μm or less.

A method of measuring the thickness of the porous base is the same as a method of measuring thickness of a hydrophilic composite porous membrane described later.

From the viewpoint of maintaining the property that the metal solution can reach the substrate by smearing while sealing the metal solution, an average pore size of the porous base measured by a perm-porometer is preferably 0.05 μm or more, more preferably 0.07 μm or more, and still more preferably 0.08 μm or more. From the viewpoint of preventing the metal solution from overflowing, the average pore size of the porous base measured by the perm-porometer is preferably 0.2 μm or less, more preferably 0.15 μm or less, and still more preferably 0.1 μm or less. The average pore size of the porous base measured by the perm-porometer is a value determined by a half-dry method specified in ASTM E1294-89 using a palm porometer, and, details of the measurement method are the same as details of the measurement method for the average pore size of the hydrophilic composite porous membrane.

The Gurley value (second/100 ml·μm) per unit thickness of the porous base is, for example, from 0.001 to 15, from 0.01 to 10, and from 0.05 to 5. The Gurley value of the porous base is a value measured according to JIS P8117: 2009.

A porosity of the porous base is, for example, from 60% to 90%, from 65% to 87%, and from 70% to 85%. The porosity of the porous base is determined according to the following calculation method. That is, when constituent materials are a, b, c, . . . , and n, the masses of the constituent materials are Wa, Wb, Wc, . . . , and Wn (g/cm²), true densities of the constituent materials are da, db, dc, . . . , and do (g/cm³), and film thickness is t (cm), a porosity ε (%) is determined by the following Formula:

ε={1−(Wa/da+Wb/db+Wc/dc+ . . . +Wn/dn)/t}×100

[Microporous Polyolefin Membrane]

One embodiment of the porous base is a microporous membrane containing polyolefin (referred to as a microporous polyolefin membrane in the disclosure). Examples of the polyolefin contained in the microporous polyolefin membrane include, but are not particularly limited to, polyethylene, polypropylene, polybutylene, polymethylpentene, and a copolymer of polypropylene and polyethylene. Among these, polyethylene is preferred, and high-density polyethylene, a mixture of high-density polyethylene and ultrahigh molecular weight polyethylene, and the like are suitable. One embodiment of the microporous polyolefin membrane is a microporous polyethylene membrane in which polyolefin contained is only polyethylene.

A weight average molecular weight (Mw) of the polyolefin contained in the microporous polyolefin membrane is, for example, from 100,000 to 5,000,000. When the Mw of the polyolefin is 100,000 or more, sufficient mechanical characteristics can be imparted to the microporous membrane. When the Mw of the polyolefin is 5,000,000 or less, it is easy to form a microporous membrane.

One embodiment of the microporous polyolefin membrane is a microporous membrane containing a polyolefin composition (in the disclosure, the polyolefin composition means a mixture of two or more polyolefins, and when the polyolefin contained is only polyethylene, the polyolefin composition is referred to as a polyethylene composition). The polyolefin composition has the effect of forming a network structure with fibrillation during drawing and increasing the porosity of the microporous polyolefin membrane.

As the polyolefin composition, a polyolefin composition containing from 5% by mass to 70% by mass, with respect to the total amount of the polyolefin, of an ultrahigh molecular weight polyethylene having a weight average molecular weight of 9×10⁵ or more is preferred, a polyolefin composition containing from 20% by mass to 65% by mass of the ultrahigh molecular weight polyethylene is more preferred, and a polyolefin composition containing from 30% by mass to 60% by mass of the ultrahigh molecular weight polyethylene is still more preferred.

The polyolefin composition is preferably a polyolefin composition in which an ultrahigh molecular weight polyethylene having a weight average molecular weight of 9×10⁵ or more and a high density polyethylene having a weight average molecular weight of from 2×10⁵ to 8×10⁵ and a density of from 920 kg/m³ to 960 kg/m³ are mixed at a mass ratio of from 5:95 to 70:30 (more preferably from 20:80 to 65:35, still more preferably from 30:70 to 60:40).

In the polyolefin composition, the overall weight average molecular weight of the polyolefin is preferably from 2×10⁵ to 4×10⁶.

The weight average molecular weight of the polyolefin constituting the microporous polyolefin membrane can be obtained by heating and dissolving the microporous polyolefin membrane in o-dichlorobenzene and performing measurement at a column temperature of 135° C. and a flow rate of 1.0 ml/min by gel permeation chromatography (system: Alliance GPC 2000 type manufactured by Waters Corporation, column: GMH6-HT and GMH6-HTL). Molecular weight monodisperse polystyrene (manufactured by Tosoh Corporation) is used for molecular weight calibration.

One embodiment of the microporous polyolefin membrane is a microporous membrane containing polypropylene from the viewpoint of providing heat resistance with which the membrane does not easily break when exposed to high temperatures.

One embodiment of the microporous polyolefin membrane is a microporous polyolefin membrane containing at least a mixture of polyethylene and polypropylene.

One embodiment of the microporous polyolefin membrane is a microporous polyolefin membrane having a multi-layer structure of two or more layers, in which at least one layer contains polyethylene and at least one layer contains polypropylene.

˜Production Method of Microporous Polyolefin Membrane˜

The production method of the microporous polyolefin membrane in the disclosure is not particularly restricted, and preferably, specifically includes the following processes (1) to (5). Polyolefin which is used as the raw material is as described above.

(1) Preparation of Polyolefin Solution

A polyolefin solution in which polyolefin is dissolved in a solvent is prepared. Examples of the solvent include paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decaline, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulphoxide, and hexane. At this time, two or more of these solvents may be used in combination.

Among the solvents, examples of the volatile solvent include solvents having a boiling point lower than 300° C. at atmospheric pressure, such as decaline, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulphoxide, hexane, tetralin, ethylene glycol, and glycerin. Examples of the nonvolatile solvent include solvents having a boiling point of 300° C. or higher at atmospheric pressure, such as paraffin, liquid paraffin, paraffin oil, mineral oil, and castor oil. As the mixed solvent, the combination of decaline and paraffin is preferred.

The concentration of the polyolefin in the polyolefin solution is preferably from 1 to 35% by mass, and more preferably from 10 to 30% by mass. When the concentration of polyolefin is 1% by mass or more, a gel composition obtained by cold gelation is hard to deform since the gel composition can be maintained so as not to highly swell by the solvent, which provides favorable handleability. On the other hand, when the concentration of polyolefin is 35% by mass or lower, the discharge rate can be maintained since the pressure during extrusion can be restrained, which provide excellent productivity.

(2) Extrusion of Polyolefin Solution

The prepared polyolefin solution is kneaded with a monoaxial extruder or a biaxial extruder, and extruded at a temperature from the melting point to the melting point+60° C. through a T-die or I-die. In this case, a biaxial extruder is preferably employed.

Then, the polyolefin solution extruded from the die is allowed to pass through a chill roll or a cooling bath to form a gel composition. In this case, it is preferred that the polyolefin solution be quenched to a temperature below the gelation temperature to be gelled.

(3) Removing Solvent

Next, the solvents are removed from the gel composition. When a volatile solvent is used in the preparation of the polyolefin solution, the solvent can also be removed from the gel composition by evaporating by heating or the like which is also served as a pre-heating process. When a nonvolatile solvent is used in the preparation of the polyolefin solution, the solvent can be removed by, for example, squeezing out by applying a pressure. The solvent need not be completely removed.

(4) Drawing of Gel Composition

After removing solvents, the gel composition is drawn. Here, prior to the drawing process, a relaxing process may be performed. In the drawing process, the gel composition is heated, and monoaxially or biaxially drawn at a predetermined magnification by using a normal tenter method, a roll method, a rolling method or a combination thereof. The biaxial drawing may be performed simultaneously or successively. The drawing may be performed in longitudinal multistep, or three- or four-step.

A drawing temperature is preferably 80° C. or higher and less than the melting point of the polyolefin which is used for the production, and more preferably from 90° C. to 130° C. When the heating temperature is less than the melting point, the gel composition is less likely to melt, which provides a favorable drawing. When the heating temperature is 80° C. or higher, the gel composition softens sufficiently and a drawing at a high magnification is possible without a membrane breakage during drawing.

The drawing magnification varies depending on the thickness of the original fabric, and is at least two times or larger, and preferably from 4 to 20 times in one axis direction.

After the drawing, a heat fixation is performed if necessary to provide a heat dimensional stability.

(5) Extraction and Removal of Solvent

The gel composition after drawing is immersed in an extraction solvent to extract a solvent, especially a nonvolatile solvent. Examples of extraction solvent include easily volatile solvent such as hydrocarbons such as pentane, hexane, heptane, cyclohexane, decaline, and tetralin; chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, and methylene chloride; fluorohydrocarbons such as trifluoroethane; and ethers such as diethyl ether and dioxane. These solvents are selected appropriately depending on the solvent which is used for preparing the polyolefin solution, particularly a nonvolatile solvent, and may be used singly or in combination. As for the extraction of the solvent, the solvent in the microporous polyolefin membrane is removed to less than 1% by mass.

[Hydrophilic Composite Porous Membrane]

The plating diaphragm of the disclosure is preferably a hydrophilic composite porous membrane having a base made of a polyolefin porous membrane and a hydrophilic material covering at least a portion of the base.

The plating diaphragm of the disclosure is preferably a hydrophilic composite porous membrane having a base made of a polyolefin porous membrane and a hydrophilic material covering at least a portion of at least a main surface, a pore inner surface, or a combination thereof, of the base, and further preferably a hydrophilic composite porous membrane having a base made of a polyolefin porous membrane and a hydrophilic material covering at least a portion of at least one main surface, a pore inner surface, or a combination thereof, of the base (i.e., at least a portion of at least one main surface and at least a portion of the pore inner surface).

—Physical Properties of Plating Diaphragm—

The plating diaphragm (preferably a hydrophilic composite porous membrane) of the disclosure has a tensile breaking strength of from 11 MPa to 300 MPa.

If the tensile breaking strength is less than 11 MPa, the diaphragm tends to break when plating is performed, and it is difficult to perform stable plating. On the other hand, when the tensile breaking strength exceeds 300 MPa, the membrane is too hard, has poor flexibility, and is inferior in handleability.

For the same reason as described above, the lower limit of the tensile breaking strength of the plating diaphragm is preferably 13 MPa or more, more preferably 15 MPa or more, and still more preferably 17 MPa or more. The upper limit of the tensile breaking strength of the plating diaphragm is preferably 100 MPa or less, more preferably 50 MPa or less, from the viewpoint of handleability.

In the measurement of the tensile breaking strength, a strip-shaped sample piece (width 15 mm, length 50 mm) is pulled at a speed of 200 mm/min with a tensile tester (manufactured by Orientec Co., Ltd., RTE-1210), and the tensile breaking strength can be obtained as tensile strength (MPa) at a time when the sample piece has broken. The measurement is performed in a first direction (e.g., MD direction) arbitrarily cut out and a second direction (e.g., TD direction) orthogonal to the first direction, and a value of lower strength is determined as the tensile breaking strength of the plating diaphragm of the disclosure.

The plating diaphragm (preferably a hydrophilic composite porous membrane) of the disclosure preferably has an average pore size of from 5 nm to 300 nm.

The average pore size is a pore size measured by a perm-porometer.

When the average pore size measured by the perm-porometer is 5 nm or more, ion conduction is easily ensured, and poor plating is unlikely to occur. When the average pore size measured by the perm-porometer is 300 nm or less, the plating solution is unlikely to leak.

From the viewpoint that a plating diaphragm having favorable ion conductivity and high uniformity is easily obtained, the average pore size is preferably 30 nm or more, more preferably 40 nm or more, and still more preferably 50 nm or more. From the viewpoint of leakage of the plating solution, the average pore size is preferably 200 nm or less, more preferably 100 nm or less, and still more preferably 80 nm or less.

Using a perm-porometer (PMI Inc., model: CFP-1500AEX), the average pore size measured by the perm-porometer can be obtained with an impregnation liquid as GALWICK (perfluoropolyether; manufactured by Porous Materials Inc., surface tension: 15.9 dyne/cm) by the half-dry method specified in ASTM E1294-89.

When only one main surface of the plating diaphragm has a hydrophilic material, the main surface having the hydrophilic material is placed facing a pressurizing portion of the perm-porometer, and measurement is performed.

The thickness of the plating diaphragm (preferably a hydrophilic composite porous membrane) is preferably 8 μm or more, more preferably 15 μm or more, still more preferably 30 μm or more, and particularly preferably 50 μm or more, from the viewpoint of easy handling and difficulty in breakage. A thickness of the hydrophilic composite porous membrane is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 120 μm or less, from the viewpoint that the plating solution easily enters the inside and easily reaches the substrate.

The thickness of the plating diaphragm can be obtained by measuring 10 points with a contact-type film thickness meter and averaging the measured values.

The Gurley value (second/100 ml·μm) per unit thickness of the plating diaphragm (preferably a hydrophilic composite porous membrane) is, for example, from 0.001 to 5, from 0.01 to 5, and from 0.05 to 5. The Gurley value of the hydrophilic composite porous membrane is a value measured according to JIS P8117: 2009.

The porosity of the plating diaphragm (preferably a hydrophilic composite porous membrane) is preferably from 60% to 90%, more preferably from 65% to 85%, and still more preferably from 70% to 80%. When the porosity of the plating diaphragm is 60% or more, the plating solution easily reaches the substrate. When the porosity of the plating diaphragm is 90% or less, favorable strength is easily obtained.

The porosity of the plating diaphragm is determined according to the following calculation method. That is, when constituent materials are a, b, c, . . . , and n, the masses of the constituent materials are Wa, Wb, Wc, . . . , and Wn (g/cm²), true densities of the constituent materials are da, db, dc, . . . , and do (g/cm³), and film thickness is t (cm), a porosity ε (%) is determined by the following Formula:

ε={1−(Wa/da+Wb/db+Wc/dc+ . . . +Wn/dn)/t}×100

It is preferable that the plating diaphragm hardly curls from the viewpoint of handleability.

From the viewpoint of suppressing curling of the plating diaphragm, the plating diaphragm is preferably a diaphragm having a hydrophilic material on each main surface of the base.

˜Production Method of Hydrophilic Composite Porous Membrane˜

The production of a hydrophilic composite porous membrane, which is an example of a plating diaphragm, will be described with reference to an example of a method in the case of using a hydrophilic resin as a hydrophilic material.

The production method of the hydrophilic composite porous membrane is not particularly limited.

Examples of a general production method of a hydrophilic composite porous membrane include a method of applying a coating solution containing a hydrophilic resin to a porous base, drying the coating solution, and covering the porous base with the hydrophilic resin; and a method of graft-polymerizing a hydrophilic monomer on a porous base and covering the porous base with a hydrophilic resin.

The coating solution containing the hydrophilic resin can be prepared by mixing and stirring the hydrophilic resin in a solvent to dissolve or disperse the hydrophilic resin in the solvent. The solvent is not particularly limited as long as it is a solvent that is a good solvent for the hydrophilic resin, and specific examples include 1-propanol aqueous solution, 2-propanol aqueous solution, N,N-dimethylformamide aqueous solution, dimethyl sulfoxide aqueous solution, and an aqueous ethanol solution. The ratio of an organic solvent in these aqueous solutions is preferably from 30% by mass to 70% by mass.

When the coating solution containing the hydrophilic resin is applied to the porous base, the concentration of the hydrophilic resin in the coating solution is preferably from 0.01% by mass to 5% by mass. When the concentration of the hydrophilic resin in the coating solution is 0.01% by mass or more, hydrophilicity can be efficiently imparted to the porous base. In this respect, the concentration of the hydrophilic resin in the coating solution is more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more. When the concentration of the hydrophilic resin in the coating solution is 5% by mass or less, the water flowrate in the produced hydrophilic composite porous membrane is high. In this respect, the concentration of the hydrophilic resin in the coating solution is more preferably 3% by mass or less, and still more preferably 2% by mass or less.

The coating solution can be applied to the porous base by a known coating method.

Examples of the coating method include a dipping method, a knife coater method, a gravure coater method, a screen printing method, a Meyer bar method, a die coater method, a reverse roll coater method, an ink jet method, a spray method, and a roll coater method. A layer of the hydrophilic resin can be formed stably by adjusting a temperature of the coating solution at the time of coating. The temperature of the coating solution is not particularly limited, but is preferably in a range of from 5° C. to 40° C.

A temperature for drying the coating solution is preferably from 25° C. to 100° C. When the drying temperature is 25° C. or higher, the time required for drying can be reduced. In this respect, a dry concentration is more preferably 40° C. or higher and still more preferably 50° C. or higher. When the drying temperature is 100° C. or lower, shrinkage of the porous base is suppressed. In this respect, the drying temperature is more preferably 90° C. or lower, and still more preferably 80° C. or lower.

The hydrophilic composite porous membrane may contain a surfactant, a wetting agent, an antifoaming agent, a pH adjuster, a coloring agent, and the like.

[Plating Apparatus and Plating Method]

The plating apparatus of the disclosure includes an anode, a plating diaphragm that is disposed between the anode and a substrate, which is a cathode, and that contains metal ions, and a power supply that applies a voltage between the anode and the substrate. In this plating apparatus, a metal derived from the metal ions is deposited on a surface of the substrate in contact with the plating diaphragm, to form a metal film on the surface of the substrate. In the plating apparatus of the disclosure, the plating diaphragm includes a base made of a polyolefin porous membrane, and in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa.

The plating method of the disclosure includes disposing a plating diaphragm between an anode and a substrate that is a cathode, applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm, and depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate. Similarly to the plating apparatus of the disclosure, in the plating method of the disclosure, the plating diaphragm includes a base made of a polyolefin porous membrane, and in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa.

In the plating apparatus and the plating method of the disclosure, since the fact that the plating diaphragm includes a base made of a polyolefin porous membrane, the contact angle θ of the plating diaphragm, and details of the tensile breaking strength of the plating diaphragm are similar to the case of the plating diaphragm described above, the description is omitted here.

One embodiment of the plating apparatus of the disclosure will be described with reference to FIGS. 1 and 2.

FIG. 1 is a schematic cross-sectional view of a film forming apparatus 1A for a metal film according to a first embodiment of the present invention. FIG. 2 is a view for explaining formation of a metal film F on a surface Ba of a substrate B using the film forming apparatus 1A shown in FIG. 1.

The film forming apparatus 1A according to the present embodiment deposits a metal by reducing metal ions, and forms a metal film made of the deposited metal on a surface of the substrate B.

The substrate B is not particularly limited as long as the surface on which the metal film is formed functions as a cathode (i.e., a surface having conductivity). In the present embodiment, the substrate B is a metal plate of aluminum, iron, or the like. In addition, the substrate B may be a substrate in which a metal layer of copper, nickel, silver, iron or the like is covered on the entire surface or a portion of the surface of a polymer resin such as an epoxy resin, ceramics, or the like, and this metal layer functions as a cathode.

The film forming apparatus 1A includes a metal anode 11, a plating diaphragm 13 disposed between the anode 11 and the substrate B (cathode), a power supply 16 which applies a voltage between the anode 11 and the substrate B, and a placing table 40 on which the substrate B is placed.

The anode 11 may be in the form of a block or a flat plate or may be made of a porous body or a mesh (mesh-like member) as long as the anode 11 has a size that covers a region where the substrate B is formed. The material of the anode 11 is the same as the material of a metal film to be formed, and is preferably an anode which is soluble in a metal solution L containing metal ions, which will be described later. Accordingly, the deposition rate of the metal film can be increased. For example, in a case in which the metal film is a copper film, it is preferable to use an oxygen-free copper plate as the material of the anode 11. Since the metal solution L before film formation contains metal ions, the anode 11 may also be an anode which is insoluble in the metal solution L.

The plating diaphragm 13 can be impregnated with (contain) the metal ions by being brought into contact with the metal solution L and is not particularly limited as long as the metal ions are reduced at the surface of the substrate B and a metal derived from the metal ions are deposited when a voltage is applied. In the present embodiment, the plating diaphragm 13 has flexibility and has a film thickness and a hardness to conform to a surface Ba of the substrate B when pressed during film formation.

As the plating diaphragm 13, the above-described plating diaphragm of the disclosure can be used. The details of the plating diaphragm are as described above, and description thereof is omitted here.

The metal solution L is a liquid (electrolyte solution; so-called “plating solution”) containing the metal of the metal film to be formed in the state of ions as described above.

As the metal, one or two or more selected from the group consisting of nickel, zinc, copper, chromium, tin, silver, gold, and lead may be used.

The metal solution L is an aqueous solution in which the above metal is dissolved (ionized) with an acid such as nitric acid, phosphoric acid, succinic acid, nickel sulfate, or pyrophosphoric acid.

In the present embodiment, the film forming apparatus 1A further includes a housing 20. In the housing 20, the metal solution L is disposed between the anode 11 and the plating diaphragm 13, and a first accommodation chamber 21 which accommodates the metal solution L to cause the metal solution L to be disposed on the surface Ba of the substrate B via the plating diaphragm 13 during film formation is formed.

In the first accommodation chamber 21, the anode 11 is disposed at a position opposing the plating diaphragm 13, and the metal solution L accommodated in the first accommodation chamber 21 is in contact with the plating diaphragm 13 and the anode 11. In the first accommodation chamber 21, a first opening 22 which has a size greater than that of the surface Ba of the substrate B on a side where the metal film is to be formed is formed. In the first accommodation chamber 21, the first opening 22 is covered with the plating diaphragm 13 in the state in which the metal solution L is accommodated between the anode 11 and the plating diaphragm 13, and the metal solution L is sealed in the first accommodation chamber 21 in a flowable state.

As described above, in the present embodiment, during film formation, the metal solution L is disposed on the surface Ba of the substrate B via the plating diaphragm 13, and the plating diaphragm 13 can conform to the surface Ba of the substrate B by the liquid pressure of the metal solution L. As the material of the housing 20, a metal material such as aluminum or stainless steel or the like may be employed, and the material thereof is not particularly limited as long as the housing 20 is not excessively deformed (rigid body) by a pressing portion 30A.

In the present embodiment, the film forming apparatus 1A is provided with the placing table 40 made of a metal, on which the substrate B is placed. The material of the placing table 40 is a metal material such as aluminum or stainless steel. However, the material thereof is not particularly limited as long as the placing table 40 is not excessively deformed (rigid body) by the pressing portion 30A.

In the placing table 40, a second accommodation chamber 41 which accommodates a fluid 45 to cause the fluid 45 to be disposed on the rear surface Bb of the substrate B positioned on the side opposite to the surface Ba on which the metal film is formed via a thin film 43 is formed. Specifically, in the second accommodation chamber 41, a second opening 42 which has a size greater than that of the rear surface Bb of the substrate B is formed. By covering the second opening 42 with the thin film 43 (film) the fluid 45 is sealed in the second accommodation chamber 41 in a flowable state.

Here, the fluid 45 is a material having fluidity, for example, a gas, a liquid, or a gel, and is not particularly limited as long as the material has a property of being cushioned from the substrate B when coming into contact with the substrate B via the thin film 43. Examples of the gas include air and an inert gas such as nitrogen gas. Examples of the liquid include water and oil. Examples of the gel include a polymer gel such as polystyrene.

In the present embodiment, the material of the thin film 43 includes a resin, a metal, or a laminate of these materials in a layer form, and the thin film 43 has flexibility. In the present embodiment, the material and the thickness of the thin film 43 are not limited as long as the thin film 43 conforms to the rear surface Bb of the substrate B when pressed during film formation and the strength thereof is secured when pressed. The thickness of the thin film 43 is preferably in a range of from 0.1 μm to 10 μm.

The negative electrode of the power supply 16 is connected to the substrate B, and the positive electrode of the power supply 16 is connected to the anode 11. In a case in which a metal layer is formed as the cathode on a part of the surface Ba of the substrate B, the metal layer is electrically connected to the negative electrode of the power supply 16, for example, via a conductor jig (not illustrated).

In the present embodiment, the film forming apparatus 1A further includes the pressing portion 30A above the housing 20. In the present embodiment, the housing 20 is movable (can be raised or lowered) by the pressing portion 30A so that the substrate B can be interposed between the plating diaphragm 13 and the thin film 43. In the present embodiment, the pressing portion 30A has (1) a function of moving (raising or lowering) the housing 20 with respect to the placing table 40 to cause the substrate B to be interposed between the plating diaphragm 13 and the thin film 43, and (2) a function of pressing the plating diaphragm 13 and the thin film 43 against the substrate B interposed between the plating diaphragm 13 and the thin film 43.

In the present embodiment, the housing 20 is movable with respect to the fixed placing table 40 by the pressing portion 30A. However, for example, by providing a pressing portion for the placing table 40, the placing table 40 can be moved with respect to the housing 20 while the housing 20 is fixed.

The pressing portion 30A is not particularly limited as long as the pressing portion 30A has the functions described in (1) and (2), and for example, a hydraulic or pneumatic cylinder may be employed. Otherwise, the pressing portion 30A may be a motor with a linear guide or the like. As described above, while causing the substrate B to be interposed between the plating diaphragm 13 and the thin film 43 and pressing the substrate B against the plating diaphragm 13 and the thin film 43 using the pressing portion 30A, a metal film can be formed.

Next, an embodiment of the plating method of the disclosure will be described using as an example a film forming method using the film forming apparatus 1A according to the present embodiment.

First, as illustrated in FIG. 1, the substrate B is disposed on the placing table 40 so that the surface Ba on which a metal film is to be formed faces the plating diaphragm 13. Specifically, the substrate B is placed on the thin film 43 of the placing table 40 so that the entirety of the rear surface Bb of the substrate B is disposed on the fluid 45 accommodated in the second accommodation chamber 41 of the placing table 40 via the thin film 43.

As described above, the metal solution L is sealed in the first accommodation chamber 21 of the housing 20 with the plating diaphragm 13 so that the metal solution L is disposed between the anode 11 and the plating diaphragm 13. The fluid 45 is sealed in the second accommodation chamber 41 of the placing table 40 with the thin film 43 so that the fluid 45 is disposed on the rear surface Bb of the substrate B via the thin film 43. A metal film is formed on the surface Ba of the substrate B by using the housing 20 and the placing table 40 described above.

Specifically, as illustrated in FIG. 2, in a state where the substrate B is placed on the placing table 40, the placing table 40 and the housing 20 are moved relative to each other, so that the substrate B is interposed between the plating diaphragm 13 and the thin film 43. Specifically, the housing 20 is lowered toward the placing table 40 by the pressing portion 30A to cause the metal solution L to be disposed on the surface Ba of the substrate B via the plating diaphragm 13. More specifically, the part of the plating diaphragm 13 positioned in the first opening 22 formed in the first accommodation chamber 21 is brought into contact with the surface Ba of the substrate B.

In the placing table 40 and the housing 20, the placing table 40 may be fixed, and the housing 20 may be moved. Alternatively, the housing 20 may be fixed, and the placing table 40 may be moved.

By pressurizing the substrate B from the plating diaphragm 13 side by the pressing portion 30A, the plating diaphragm 13 and the thin film 43 are pressed against the substrate B in the state of being interposed between the plating diaphragm 13 and the thin film 43. Accordingly, the plating diaphragm 13 and the thin film 43 can conform to the surface Ba and the rear surface Bb of the substrate B. Here, if a pressure gauge (not illustrated) for measuring the pressure of the metal solution L is provided in the first accommodation chamber 21, the substrate B can be pressed at a predetermined pressure while checking the measured pressure.

In this state, a voltage is applied between the anode 11 and the substrate B by the power supply 16 to reduce the metal ions contained in the plating diaphragm 13, thereby causing a metal derived from the metal ions to deposit on the surface Ba of the substrate B. Accordingly, the metal film F is formed on the surface Ba of the substrate B.

As described above, when the metal film F is formed, the plating diaphragm 13 and the thin film 43 conform to the surface Ba and the rear surface Bb of the substrate B, the surface Ba of the substrate B is uniformly pressurized by the metal solution L via the plating diaphragm 13, and the rear surface Bb of the substrate B is uniformly pressurized by the fluid 45 via the thin film 43. Accordingly, the plating diaphragm 13 and the thin film 43 can be uniformly pressed against the substrate B without forming a gap from the surface Ba and the rear surface Bb of the substrate B. In this state, by applying a voltage between the anode 11 and the substrate B, the metal ions contained in the plating diaphragm 13 are reduced, the metal derived from the metal ions is deposited on the surface Ba of the substrate B, and the metal film F having a uniform film thickness can be formed on the surface Ba of the substrate B.

Example

Hereinafter, the embodiment of the present invention will be more specifically described using specific examples. However, the disclosure is not limited to the following examples within the scope not departing from the gist thereof.

(Measurement Method)

Methods of measurement and evaluation performed on hydrophilic composite porous membranes and plating diaphragms of the following Examples and Comparative Examples are shown below.

—Membrane Thickness—

The membrane thicknesses of the microporous polyolefin membrane was obtained by measuring the thicknesses at 10 points by a contact-type film thickness meter (manufactured by Mitutoyo Corporation, Lightmatic VL-50A) and averaging the measured values. Here, a contact probe having a cylindrical shape and a diameter of the bottom surface of 0.5 cm was used. During the measurement, adjustments were made such that a load of 0.01 N was applied.

—Average Pore Size—

A mean flow pore size (nm) as the average pore size of the microporous polyolefin membrane was measured by using a perm-porometer (model: CFP-1500 AEX) manufactured by Porous Materials Co., Ltd. and GALWICK (perfluoropolyether; manufactured by Porous Materials Co., Ltd. surface tension: 15.9 dyne/cm) as an impregnating solution, based on the half-dry method specified in ASTM E1294-89.

As the measurement conditions, the temperature was set to 25° C., and the pressure was set to from 100 kPa to 1000 kPa.

—Porosity—

The porosity (ε) of the microporous polyolefin membrane was calculated by the following Formula:

ε(%)=(t−Ws/ds)/t×100

Ws: Basis weight of microporous polyolefin membrane (g/m²)

ds: True density of polyolefin (g/cm³)

t: Thickness of microporous polyolefin membrane (μm)

The basis weight of the microporous polyolefin membrane was determined by measuring the mass of a sample cut out to a size of 10 cm×10 cm and dividing the mass by the area.

—Contact Angle θ—

The static contact angle was measured using, as a measurement device, a fully automatic contact angle meter (DMo-701FE and Interface Measurement and Analysis System FAMAS) manufactured by Kyowa Interface Science, Inc.

In the measurement, 4 μl of pure water was dropped on a surface of a hydrophilic composite porous membrane (plating diaphragm) after hydrophilic treatment of a microporous polyethylene membrane or a surface of a microporous polyethylene membrane subjected to no hydrophilic treatment, and the contact angle θ between a droplet of the pure water and the surface of the microporous polyethylene membrane after one second has passed since landing of the droplet of the pure water on the surface was measured in the atmosphere under normal pressure at a temperature of 24° C. and a relative humidity of 60%.

—Gurley Value—

The Gurley value (sec/100 ml) of a microporous polyolefin membrane having an area of 642 mm² was measured in accordance with Japanese Industrial Standards (JIS) P8117.

—Tensile Breaking Strength—

A strip-shaped sample piece (width 15 mm, length 50 mm) cut out in parallel to each of the MD and TD directions was pulled at a speed of 200 mm/min with a tensile tester (manufactured by Orientec Co., Ltd., RTE-1210), and the tensile strength (MPa) was obtained at a time when the sample piece has broken. A lower one of the tensile strengths determined in the MD and TD directions was defined as the tensile breaking strength.

—Surface Structure of Metal Film—

A surface structure of a metal film was observed using a microscope (manufactured by Keyence Corporation, VH-8000) and evaluated according to the following evaluation criteria. The surface structure of the metal film was evaluated by defining criteria A and B as allowable ranges.

<Evaluation Criteria of Surface Structure>

A: No bubbles and peeling are observed, and uniformity of the surface of the metal film is excellent.

B: Slight occurrence of bubbles or peeling is observed, but it was not a practically problematic level.

C: Bubbles and peeling are observed, and a uniform metal film cannot be formed.

—Cathode Current Efficiency of Metal Film—

Cathode current efficiency in a nickel (Ni) film and a copper (Cu) film was obtained from the following Formula, and evaluated according to the following evaluation criteria. The cathode current efficiency in the Ni film was evaluated by defining criteria A and B as allowable ranges. The cathode current efficiency in the Cu film was evaluated by defining criteria D and E as allowable ranges.

Cathode current efficiency (%)=Mass of metal of metal film/theoretical deposition amount based on Faraday's law of electrolysis×100

<Evaluation Criteria of Cathode Current Efficiency in Ni Film>

A: During film formation at a current density of 50 mA/cm², the cathode current efficiency is 90% or more.

B: During film formation at a current density of 50 mA/cm², the cathode current efficiency is 80% or more and less than 90%.

C: During film formation at a current density of 50 mA/cm², the cathode current efficiency is less than 80%.

<Evaluation Criteria of Cathode Current Efficiency in Cu Film>

D: During film formation at a current density of 23 mA/cm², the cathode current efficiency is 90% or more.

E: During film formation at a current density of 23 mA/cm², the cathode current efficiency is 80% or more and less than 90%.

F: During film formation at a current density of 23 mA/cm², the cathode current efficiency is less than 80%.

Example 1

—Preparation of Microporous Polyethylene Membrane—

A microporous polyethylene membrane (thickness: 100 μm, average pore size: 85 nm, Gurley value: 40 sec/100 ml, tensile breaking strength: 20 MPa) produced as described below was used as a base.

<Production of Microporous Polyethylene Membrane>

A polyethylene composition in which 12.25 parts by mass of ultrahigh molecular weight polyethylene (hereinafter, referred to as “UHMWPE”) having a weight average molecular weight of 4,600,000 and 10.75 parts by mass of high density polyethylene (hereinafter, referred to as “HDPE”) having a weight average molecular weight of 560,000 and a density of 950 kg/m³ were mixed was provided. The polyethylene composition and decalin were mixed at a polymer concentration of 25% by mass to prepare a polyethylene solution.

The polyethylene solution was extruded in the shape of a sheet from a die at a temperature of 153° C., and the extrudate obtained was then cooled in a water bath at a water temperature of 20° C. to obtain a first gel-like sheet.

The first gel-like sheet was pre-dried for 10 minutes under a temperature atmosphere of 70° C., then subjected to primary drawing in the MD direction at a magnification of 1.45 times, and then completely dried under a temperature atmosphere of 57° C. for 5 minutes to obtain a second gel-like sheet (base tape) (a residual amount of a solvent in the second gel-like sheet was less than 30% by mass). Next, as secondary drawing, the second gel-like sheet (base tape) was drawn in the MD direction at a temperature of 90° C. at a magnification of 3 times, then drawn in the TD direction at a temperature of 130° C. at a magnification of 9 times, and immediately thereafter heat-treated (heat-fixed) at 132° C.

The heat-fixed sheet was immersed in a two-tank methylene chloride bath successively for 30 seconds per tank, thereby extracting decalin in the sheet. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40° C.

As described above, a microporous polyethylene membrane was obtained.

—Preparation of Coating Solution—

As a hydrophilic resin that is a hydrophilic material, ethylene/vinyl alcohol binary copolymer (manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., Soarnol DC3203R, ethylene unit: 32 mol %, hydroxy group-containing olefin/vinyl alcohol resin; hereinafter, referred to as EVOH) was provided.

EVOH was dissolved in a mixed solvent of 1-propanol and water (1-propanol:water=3:2 [volume ratio]) so that the concentration of EVOH was 0.2% by mass, to obtain a coating solution.

—Production of Hydrophilic Composite Porous Membrane—

The microporous polyethylene membrane fixed to a metal frame was immersed in a coating solution for 20 minutes to impregnate the coating solution into pores of the microporous polyethylene membrane, and then the microporous polyethylene membrane was pulled up. Next, an excess coating solution attached to both main surfaces of the microporous polyethylene membrane was removed, and dried at room temperature for 2 hours. Next, the metal frame was removed from the microporous polyethylene membrane.

As described above, a hydrophilic composite porous membrane having a thickness of 80 μm was obtained in which both the main surfaces and the pore inner surface of the microporous polyethylene membrane were covered with the hydrophilic resin layer.

Table 1 collectively shows various physical properties of the hydrophilic composite porous membrane (plating diaphragm) and the microporous polyethylene membrane.

—Formation of Metal Film—

A film forming apparatus having the same configuration as in FIG. 1 was prepared, and the 80 μm-thick hydrophilic composite porous membrane obtained above was used as a plating diaphragm. Then, a nickel (Ni) film or a copper (Cu) film was formed as a metal film by the following method.

(1) Ni Film Formation

In the film forming apparatus, foamed nickel was provided as an anode, and a copper (Cu) block of 35 mm long×18 mm wide×3 mm thick was provided as a substrate and used as a cathode. As a plating bath (metal solution), an aqueous nickel acetate solution (pH 4.0 at 25° C.) containing 1 mol/l of nickel chloride and acetic acid was provided and accommodated in the first accommodation chamber.

Then, the foamed nickel was disposed as an anode in a housing forming the first accommodation chamber for accommodating a plating solution, and a hydrophilic composite porous membrane (plating diaphragm) was disposed between the anode and the substrate which was a cathode. Then, while a surface of the substrate was brought into contact with the hydrophilic composite porous membrane, film formation was performed by applying a voltage between the anode of the film forming apparatus and the substrate under the following plating conditions.

<Plating Conditions>

Pressing force: 1.0 kN

Temperature: 60° C.

Current value: 100 mA

Time: 300 sec

Area: 10 mm×20 mm

The voltage application gradually reduced Ni ions permeating through the accommodated plating solution and contained in the plating diaphragm, and Ni metal was deposited on a surface of the Cu block in contact with the hydrophilic composite porous membrane to form an Ni film (metal film) having a thickness of 5 μm.

FIG. 3 shows a microscope photograph of the Ni film.

(2) Cu Film Formation

In the film forming apparatus, a copper mesh was provided as an anode, and a nickel (Ni) block of 50 mm long×40 mm wide×5 mm thick was provided as a substrate and used as a cathode. As a plating bath (metal solution), a 1 mol/l aqueous solution of copper sulfate was provided and accommodated in the first accommodation chamber.

Then, the copper mesh was disposed as an anode in a housing forming the first accommodation chamber for accommodating a plating solution, and a hydrophilic composite porous membrane (plating diaphragm) was disposed between the anode and the substrate which was a cathode. Then, while a surface of the substrate was brought into contact with the hydrophilic composite porous membrane, film formation was performed by applying a voltage between the anode of the film forming apparatus and the substrate under the following plating conditions.

<Plating Conditions>

Pressing force: 1.0 kN

Temperature: 60° C.

Current value: 23 mA

Time: 480 sec

Area: 10 mm×10 mm

The voltage application gradually reduced Cu ions permeating through the accommodated plating solution and contained in the plating diaphragm, and Cu metal was deposited on a surface of the Ni block in contact with the hydrophilic composite porous membrane to form a Cu film (metal film) having a thickness of 4 μm.

FIG. 4 shows a microscope photograph of the Cu film.

The Ni film and the Cu film formed as described above were measured and evaluated, and the evaluation results are shown in Table 1 below.

Example 2

As a base, a microporous polyethylene membrane having a thickness of 80 μm, an average pore size of 75 nm, a Gurley value of 110 sec/100 ml, and a tensile breaking strength of 25 MPa was provided as follows.

˜Production of Microporous Polyethylene Membrane˜

A polyethylene composition prepared by mixing 11.25 parts by mass of UHMWPE and 13.75 parts by mass of HDPE was provided. The polyethylene composition and decalin were mixed at a polymer concentration of 25% by mass to prepare a polyethylene solution.

The polyethylene solution was extruded in the shape of a sheet from a die at a temperature of 163° C., and the extrudate obtained was then cooled in a water bath at a water temperature of 20° C. to obtain a first gel-like sheet.

The first gel-like sheet was pre-dried for 10 minutes under a temperature atmosphere of 70° C., then subjected to primary drawing in the MD direction at a magnification of 1.2 times, and then completely dried under a temperature atmosphere of 57° C. for 5 minutes to obtain a second gel-like sheet (base tape) (the residual amount of a solvent in the second gel-like sheet was less than 30% by mass). Next, as secondary drawing, the second gel-like sheet (base tape) was drawn in the MD direction at a temperature of 90° C. at a magnification of 4 times, then drawn in the TD direction at a temperature of 135° C. at a magnification of 15 times, and immediately thereafter heat-treated (heat-fixed) at 142° C.

The heat-fixed sheet was immersed in a two-tank methylene chloride bath successively for 30 seconds per tank, thereby extracting decalin in the sheet. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40° C.

As described above, a microporous polyethylene membrane was obtained.

Then, a hydrophilic composite porous membrane having a thickness of 55 μm was obtained by hydrophilizing the microporous polyethylene membrane in the same manner as in Example 1, and an Ni film and a Cu film were formed in the same manner as in Example 1 using the obtained hydrophilic composite porous membrane and measured and evaluated. Table 1 below shows the physical properties and evaluation results of the microporous polyethylene membrane, the plating diaphragm (hydrophilic composite porous membrane), the Ni film and the Cu film.

FIGS. 5 and 6 each show microscope photographs of the Ni film and the Cu film.

Comparative Example 1

The same microporous polyethylene membrane as in Example 2 was provided as a base.

An Ni film and a Cu film were formed in the same manner as in Example 1 and measured and evaluated, except that a microporous polyethylene membrane was used instead of the hydrophilic composite porous membrane as the plating diaphragm in Example 1.

Table 1 below shows the physical properties and evaluation results of the plating diaphragm, the Ni film, and the Cu film.

FIGS. 7 and 8 each show microscope photographs of the Ni film and the Cu film.

Comparative Example 2

As a base, a microporous polyethylene membrane having a thickness of 25 μm, an average pore size of 70 nm, a Gurley value of 60 sec/100 ml, and a tensile breaking strength of 15 MPa was provided as follows.

˜Production of Microporous Polyethylene Membrane˜

A polyethylene composition prepared by mixing 10.2 parts by mass of UHMWPE and 6.8 parts by mass of HDPE was provided. The polyethylene composition, 82.9% by mass of paraffin, and 0.1% by mass of decalin were mixed at a polymer concentration of 17% by mass to prepare a polyethylene solution.

The polyethylene solution was extruded in the shape of a sheet from a die at a temperature of 150° C., and the extrudate obtained was then cooled in a water bath at a water temperature of 20° C. to obtain a gel-like sheet.

The gel-like sheet was drawn in the TD direction at a temperature of 105° C. at a magnification of 9 times, and immediately thereafter heat-treated (heat-fixed) at 140° C.

The heat-fixed sheet was immersed in a two-tank methylene chloride bath successively for 30 seconds per tank, thereby extracting paraffin in the sheet. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40° C.

As described above, a microporous polyethylene membrane was obtained.

An Ni film and a Cu film were formed in the same manner as in Example 1 and measured and evaluated, except that a microporous polyethylene membrane was used instead of the hydrophilic composite porous membrane as the plating diaphragm in Example 1.

Table 1 below shows the physical properties and evaluation results of the plating diaphragm, the Ni film, and the Cu film.

FIGS. 9 and 10 each show microscope photographs of the Ni film and the Cu film.

Comparative Example 3

As a base, a microporous polyethylene membrane having a thickness of 50 μm, an average pore size of 100 nm, a Gurley value of 70 sec/100 ml, and a tensile breaking strength of 10 MPa was provided as follows.

˜Production of Microporous Polyethylene Membrane˜

A polyethylene composition prepared by mixing 6.8 parts by mass of UHMWPE and 10.2 parts by mass of HDPE was provided. The polyethylene composition, 82.9% by mass of paraffin, and 0.1% by mass of decalin were mixed at a polymer concentration of 17% by mass to prepare a polyethylene solution.

The polyethylene solution was extruded in the shape of a sheet from a die at a temperature of 156° C., and the extrudate obtained was then cooled in a water bath at a water temperature of 20° C. to obtain a gel-like sheet.

The gel-like sheet was drawn in the TD direction at a temperature of 105° C. at a magnification of 9 times, and immediately thereafter heat-treated (heat-fixed) at 136° C.

The heat-fixed sheet was immersed in a two-tank methylene chloride bath successively for 30 seconds per tank, thereby extracting paraffin in the sheet. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40° C.

As described above, a microporous polyethylene membrane was obtained.

An Ni film and a Cu film were formed in the same manner as in Example 1 and measured and evaluated, except that a microporous polyethylene membrane was used instead of the hydrophilic composite porous membrane as the plating diaphragm in Example 1.

Table 1 below shows the physical properties and evaluation results of the plating diaphragm, the Ni film, and the Cu film.

FIGS. 11 and 12 each show microscope photographs of the Ni film and the Cu film.

Comparative Example 4

As a base, a microporous polyethylene membrane having a thickness of 40 μm, an average pore size of 80 nm, a Gurley value of 40 sec/100 ml, and a tensile breaking strength of 35 MPa was provided as follows.

˜Production of Microporous Polyethylene Membrane˜

A polyethylene composition prepared by mixing 12.25 parts by mass of UHMWPE and 10.75 parts by mass of HDPE was provided. The polyethylene composition and decalin were mixed at a polymer concentration of 25% by mass to prepare a polyethylene solution.

The polyethylene solution was extruded in the shape of a sheet from a die at a temperature of 153° C., and the extrudate obtained was then cooled in a water bath at a water temperature of 20° C. to obtain a first gel-like sheet.

The first gel-like sheet was pre-dried for 10 minutes under a temperature atmosphere of 70° C., then subjected to primary drawing in the MD direction at a magnification of 1.45 times, and then completely dried under a temperature atmosphere of 57° C. for 5 minutes to obtain a second gel-like sheet (base tape) (a residual amount of a solvent in the second gel-like sheet was less than 30% by mass). Next, as secondary drawing, the second gel-like sheet (base tape) was drawn in the MD direction at a temperature of 90° C. at a magnification of 6 times, then drawn in the TD direction at a temperature of 130° C. at a magnification of 9 times, and immediately thereafter heat-treated (heat-fixed) at 132° C.

The heat-fixed sheet was immersed in a two-tank methylene chloride bath successively for 30 seconds per tank, thereby extracting decalin in the sheet. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40° C.

As described above, a microporous polyethylene membrane was obtained.

The obtained microporous polyethylene membrane was subjected to a plasma treatment as a hydrophilic treatment. Various physical properties were measured using this membrane as a plating diaphragm, and the results are shown in Table 1. However, the obtained plating diaphragm had low strength and could not be evaluated for plating. “-” in Comparative Example 4 in Table 1 indicates that it is not measured.

TABLE 1 Example Example Comparative Comparative Comparative Comparative 1 2 Example 1 Example 2 Example 3 Example 4 Base Average pore 85 75 75 70 100  80 size [nm] Thickness [μm] 100 80 80 25 50 40 Porosity [%] 80 75 75 65 70 80 Gurley value 40 110 110  60 70 40 [sec/100 ml] Tensile breaking 20 25 25 15 10 35 strength [MPa] Plating Average pore 75 70 — — — 140 diaphragm size [nm] Thickness [μm] 80 55 — — — 40 Tensile breaking 25 35 — — — 5 strength [MPa] Contact angle Θ 10 15 120  115  115  5 Hydrophilization Presence P Absence A A P of base (P) (A) Evaluation Nickel Surface structure A B C C C — for plating Current efficiency A B C A A — Copper Surface structure A A C C C — Current efficiency D D D E D —

As shown in Table 1, in Examples 1 and 2, compared to Comparative Examples 1 to 3 using a hydrophobic plating diaphragm having a contact angle θ of more than 90°, in both cases of the Ni film and the Cu film, a metal film having a favorable surface structure was obtained, and the current efficiency was also favorable.

REFERENCE SIGNS LIST

-   1A: Film forming apparatus -   11: Anode -   13: Plating diaphragm -   16: Power supply -   20: Housing -   21: First accommodation chamber -   30A: Pressing portion -   30B: Pump (Pressing portion) -   40: Placing table -   41: Second accommodation chamber -   43: Thin film -   45: Fluid -   B: Substrate -   F: Metal film -   L: Metal solution 

What is claimed is:
 1. A plating diaphragm used for a plating method comprising disposing the plating diaphragm between an anode and a substrate that is a cathode, applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm, and depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate, the plating diaphragm comprising: a base made of a polyolefin porous membrane, wherein, in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength is from 11 MPa to 300 MPa.
 2. The plating diaphragm according to claim 1, wherein an average pore size of the plating diaphragm is from 5 nm to 300 nm.
 3. The plating diaphragm according to claim 1, wherein a thickness of the plating diaphragm is from 8 μm to 200 μm.
 4. The plating diaphragm according to claim 1, wherein the base has a hydrophilic material on at least a portion of a main surface, a pore inner surface, or a combination thereof.
 5. The plating diaphragm according to claim 4, wherein the hydrophilic material has at least one selected from the group consisting of a hydroxy group, a carbonyl group, a carboxy group, a formyl group, a sulfo group, a sulfonyl group, a thiol group, an amino group, a nitrile group, a nitro group, a pyrrolidone ring group, an ether bond and an amide bond.
 6. The plating diaphragm according to claim 4, wherein the hydrophilic material includes an olefin/vinyl alcohol resin.
 7. The plating diaphragm according to claim 1, wherein the metal is at least one selected from the group consisting of nickel, zinc, copper, chromium, tin, silver, gold and lead.
 8. A plating method comprising: disposing a plating diaphragm between an anode and a substrate that is a cathode; applying a voltage between the anode and the substrate, in a state in which a surface of the substrate is in contact with the plating diaphragm, to reduce metal ions contained in the plating diaphragm; and depositing a metal derived from the metal ions on the surface of the substrate, to form a metal film on the surface of the substrate, wherein the plating diaphragm comprises a base made of a polyolefin porous membrane, and wherein, in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa.
 9. A plating apparatus comprising: an anode; a plating diaphragm that is disposed between the anode and a substrate, which is a cathode, and that contains metal ions; and a power supply that applies a voltage between the anode and the substrate, a metal that is derived from the metal ions being deposited on a surface of the substrate in contact with the plating diaphragm, to form a metal film on the surface of the substrate, wherein the plating diaphragm comprises a base made of a polyolefin porous membrane, and in a case in which pure water is dropped on a surface of the plating diaphragm, a contact angle θ between a droplet of the pure water and the surface of the plating diaphragm after one second has passed since landing of the droplet of the pure water on the surface is from 0° to 90°, and a tensile breaking strength of the plating diaphragm is from 11 MPa to 300 MPa. 